This invention resides in the construction and use of catheters for interventional procedures in such fields as cardiology, neurology, urology and gastroenterology. Design features are incorporated in these catheters to facilitate their use in: (1) the advancement of the catheter through a patient's bodily passages to reach specific sites in vessels or chambers of interest; (2) correct placement of the catheter's distal tip at a targeted site within the patient, and finally (3) holding the catheter at a targeted site while procedures with other devices are completed including while the site moves in response to normal bodily functions such as breathing or a heart beat.
Guide catheters are one type of catheter utilized in these procedures. Guide catheters are relatively large lumen catheters used to guide smaller diameter catheters such as therapeutic, diagnostic or imaging catheters into bodily passages that are curved or branched. More specifically, guide catheters provide a conduit for at least a portion of the path followed by these additional catheters to desired target sites within a patient's vasculature or other body lumen or organ. In order for the catheter to be effective, however, the catheter must be able to traverse the tortuous pathways of a patient's vasculature or other anatomy in a manner as atraumatic as possible.
In order to function efficiently, guide catheters generally have a relatively stiff main body portion and a relatively soft distal portion. The stiff main body portion gives the guide catheter sufficient pushability and torqueability to allow the guide catheter to be inserted percutaneously into an artery, moved and rotated in the vasculature to position the distal end of the catheter at the desired site. However, the distal portion should have sufficient flexibility so that it can track over a guide wire and be maneuvered through a tortuous path to the treatment site. In addition, a soft distal tip at the very end of the catheter should be used to minimize the risk of causing trauma to a blood vessel while the guide catheter is being moved through the vasculature to the proper position.
Thus, to limit insertion time and discomfort to a patient, a catheter must be stiff enough to resist the formation of kinks, while at the same time, the catheter must possess flexibility to be responsive to maneuvering forces when guiding the catheter through the vascular system. In addition to these features, catheters must be designed to reach a targeted site and maintain the position at that site throughout the procedure. Guide catheters typically have preformed bends formed along their distal portion to facilitate both the placement of the distal end of the guide catheter and to the ostium of a particular coronary artery of a patient and to remain stable once in position. Likewise, angiographic catheters, which are used in evaluating the progress of coronary artery disease in patients, generally have a desired distal end curvature configuration to facilitate both the steering of the catheter to a particular artery to be examined and to provide a stable positioning of the catheter's distal portion.
As stated above, improved stabilization of a catheter's position is often achieved through curves or bends imparted to the catheter by the manufacturer. Some of these pre-formed curves function by anchoring the catheter against an opposing wall within a patient's vasculature or other anatomy. Proper anchoring is often achieved by matching the predisposed shape of the catheter with the general shape of the targeted site. Often a curve is imparted to the distal end of a catheter with the intention of placing the catheter's distal opening at a desired location in the vessel, or alternatively, on the vessel wall. A guide catheter especially designed for a procedure in a coronary artery, for example, is shaped such that when the guide catheter is inserted into the femoral artery and through the aorta of a patient, the curvature of the catheter will place its distal tip inside one of the coronary ostia. Thus, a guide catheter for the right coronary artery is shaped differently than one for the left coronary artery. A guide catheter designed to provide access to a carotid artery is again shaped differently. Likewise, guide catheters of still other shapes are designed for other bodily passages and regions of interest. Further, there are differences between patients' body structures which require varying sizes of each curve type.
Guide catheters currently available from manufacturers are designed in a variety of shapes specific for different bodily passages and procedures. Those of skill in the art recognize these different shapes by names such as Judkins Right, Judkins Left, Amplatz Right, Amplatz Left, Bentson, Shepherd Hook, Cobra, Headhunter, Sidewinder, Newton, Sones and others, each formed in a different shape. Most of these different shapes are manufactured in gradations of size and/or curvature to accommodate differences among individual patients.
When a guide catheter is inserted and advanced within a patient, its pre-formed curved shape is often distorted by the tortuous vasculature and connecting passages of a patient's vasculature. The bends must essentially become straight as the catheter is slowly advanced within the anatomy, usually over a guidewire. In order for the pre-formed manufactured curves or bends to be effective in properly seating the guide catheter, however, the imparted curves must be capable of returning their pre-formed shape or at least a predictable variant of the original shape. This is referred to herein as curve retention. Similarly, after the guide catheter is properly seated, the curves of the catheter must retain the catheter's positioning despite the constant movements in response to normal bodily functions such as breathing or a heartbeat or when other devices are passed through the lumen of the positioned catheter.
Manufacturers, therefore, often add filler material, or alternatively, use stiffer materials in curved regions to increase curve retention. Although adding materials achieves better curve retention upon placement, decreasing the catheter's flexibility in curved regions causes significant alterations in the catheter's overall performance. Specifically, the catheter's trackability is often affected. For guide catheters having curves imparted within the distal regions of the catheter, the effect in trackability performance can be quite significant. Thus, it is a goal of the present invention to create a catheter design having exceptional curve retention without diminishing the catheter's flexibility and overall trackability performance.